Single junction binary all-small-molecule (ASM) organic solar cells (OSCs) with power conversion efficiency (PCE) beyond 14% are achieved by using non-fullerene acceptor Y6 as the electron acceptor, but still lag behind that of polymer OSCs. Herein, an asymmetric Y6-like acceptor, BTP-FCl-FCl, is designed and synthesized to match the recently reported high performance small molecule donor BTR-Cl, and a record efficiency of 15.3% for single-junction binary ASM OSCs is achieved. BTP-FCl-FCl features a F,Cl disubstitution on the same end group affording locally asymmetric structures, and so has a lower total dipole moment, larger average electronic static potential, and lower distribution disorder than those of the globally asymmetric isomer BTP-2F-2Cl, resulting in improved charge generation and extraction. In addition, BTP-FCl-FCl based active layer presents more favorable domain size and finer phase separation contributing to the faster charge extraction, longer charge carrier lifetime, and much lower recombination rate. Therefore, compared with BTP-2F-2Cl, BTP-FCl-FCl based devices provide better performance with FF enhanced from 71.41% to 75.36% and J sc increased from 22.35 to 24.58 mA cm −2 , leading to a higher PCE of 15.3%. The locally asymmetric F, Cl disubstitution on the same end group is a new strategy to achieve high performance ASM OSCs.

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Y6 and its derivatives have greatly improved the power conversion efficiency (PCE) of organic photovoltaics (OPVs). Further developing high‐performance Y6 derivative acceptor materials through the relationship between the chemical structures and properties of these materials will help accelerate the development of OPV. Here, machine learning and quantum chemistry are used to understand the structure–property relationships and develop new OPV acceptor materials. By encoding the molecules with an improved one‐hot code, the trained machine learning model shows good predictive performance, and 22 new acceptors with predicted PCE values greater than 17% within the virtual chemical space are screened out. Trends associated with the discovered high‐performing molecules suggest that Y6 derivatives with medium‐length side chains have higher performance. Further quantum chemistry calculations reveal that the end acceptor units mainly affect the frontier molecular orbital energy levels and the electrostatic potential on molecular surface, which in turn influence the performance of OPV devices. A series of promising Y6 derivative candidates is screened out and a rational design guide for developing high‐performance OPV acceptors is provided. The approach in this work can be extended to other material systems for rapid materials discovery and can provide a framework for designing novel and promising OPV materials.

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